The present invention relates to a device for actuating a hydraulic power steering system for automotive vehicles having the following features:
A steering shaft, non-rotatably coupled with the steering wheel, is furnished with a pinion and is supported in a sleeve, PA1 The pinion is engaged with a gear rack coupled to the wheels to be steered, PA1 The sleeve is supported in a steering gear housing so as to be pivotable about an axis, parallel in relation to the steering shaft, and it comprises a recess to enable the pinion to engage into the gear rack, and on it a pin-shaped extension is secured perpendicularly relative to the steering shaft, the extension actuating the valve slide of a steering valve designed as a linear slide valve, and PA1 A spring which presses the gear rack against the pinion and simultaneously stabilizes the support of the sleeve in the steering gear housing. PA1 The bearing between the sleeve and the steering gear housing is formed by two needles, PA1 The two needle bearings are disposed on different sides of the gear rack, and PA1 The bearing axis of the two needle bearings is farther away from the steering shaft center line than the point of force transmission between pinion and gear rack, and it is placed on the same side of the steering shaft center line as the latter point, and the valve slide is biassed by a captivated spring.
A device of this type is known from European patent application 0 291 155. In this prior art device, the sleeve is supported on that side of the steering shaft in the housing which is remote from the gear rack. The bearing is formed by a spherical indentation in the extension and a spherical shell-shaped recess in the steering gear housing. A disadvantage of this device is that high friction forces occur in the bearing because of the great radius of effect the friction force has due to the spring being pressed on. However, the strong spring is required to ensure freedom of play between gear rack and pinion. Further, the system has a tendency of being unstable since the force of the spring, which keeps the gear rack in contact with the pinion, induces a rolling motion of the steering shaft on the gear rack, the steering valve being actuated as a result. This might be a safety risk since the vehicle would be steered inadvertently in such a case.